This application is for core support for the Penn Population Studies Center (PSC), which has fostered research and training in population since 1962. The PSC is characterized by remarkable continuity in its production of high-quality research even as the composition of its own population of Research Associates has changed and their research interests have evolved. The current PSC Research Associates are younger, more diverse, more interdisciplinary and more productive in terms of publications in major journals and receipt of major grants than those at our last competitive P30 renewal in 1998. Since 1998 the PSC has ranked first or second among all population centers in terms of publications in major general population, economics and sociology journals and NIH research awards, indicators that are very promising for future research productivity. The PSC's current research activities are concentrated on seven signature themes that relate to two aspects of population composition (endowments, human resources) and five cross-cutting approaches to the demographic triad (fertility, mortality, migration) and population composition (methods/data, temporal processes, contexts, policy evaluation, international). The proposed support for the PSC Administrative, Computing, Information Technology, and Information Dissemination (CITID), Developmental and Public Infrastructure reflects forward-looking re-evaluations of how best to use R24 and leveraged resources to provide basic, but in some respects innovative, support for the pursuit of the basic PSC central scientific objectives.